This year’s top questions mainly focused on hazards, with earthquake questions being the most frequent.

The most commonly visited FAQ was: Can you predict earthquakes? The answer is no, neither the USGS nor any other scientists have ever predicted a major earthquake. They do not know how, and they do not expect to know how any time in the foreseeable future. However based on scientific data, probabilities can be calculated for potential future earthquakes. And USGS is working on an earthquake early warning system that may eventually provide seconds-to-minutes of advance warning.

Seismographs at the U.S. Geological Survey record (1) north-south horizontal, (2) east-west horizontal, and (3) vertical components of the earthquake.

“How do volcanoes erupt?” broke up the list of earthquake questions, with most visits to that FAQ page coming after the eruption of Kileaua Volcano in Hawaii that began on June 27. And then it was back to earthquakes: Can animals predict earthquakes? Although there is anecdotal evidence of animals exhibiting strange behavior, consistent and reliable behavior before a seismic event has not been documented

A key question about safety during an earthquake was also quite frequently visited, with people wondering, “What should I do during an earthquake?” What you should do varies a bit based on where you are, inside, outside, driving, or in a mountainous area. And after an earthquake there are also steps you can take to protect yourself.

And then we were back to volcanoes: What are the different types of volcanoes? And How many active volcanoes are there on Earth? First some basics: The largest and most explosive volcanic eruptions eject tens to hundreds of cubic kilometers of magma onto the Earth’s surface. When such a large volume of magma is removed from beneath a volcano, the ground subsides or collapses into the emptied space, to form a huge depression called a caldera. Some calderas are more than 25 kilometers in diameter and several kilometers deep.

Cinder cones are the simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent.

Some of the Earth’s grandest mountains Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta in California, Mount Hood in Oregon, Mount St. Helens and Mount Rainier in Washington are composite volcanoes — sometimes called stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs and may rise as much as 8,000 feet above their bases.

And how many active volcanoes are there? There are about 1500 potentially active volcanoes, and about 500 have erupted in historical time.

We’ll finish of the most frequently visited FAQs list with: “What is the difference between a tsunami and a tidal wave? Good question. Both are sea waves, but a tsunami and a tidal wave are two different and unrelated phenomenona. A tidal wave is the wave motion of the tides. A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth. Tsunamis are ocean waves triggered by large earthquakes that occur near or under the ocean, volcanic eruptions, submarine landslides, and by onshore landslides in which large volumes of debris fall into the water. Tsunamis cause major damage and loss of life. “Tidal wave” used to be the popular term for what are actually tsunamis.

A drill rig in the Permian Basin of West Texas being used to drill a well which will be hydraulically fractured to produce natural gas. A sound control wall can be seen in the rear of the drill pad to reduce the amount of noise reaching surrounding areas. Photo Credit: Hannah Hamilton, USGS

USGS has over 1400 FAQ pages that answer questions from biology to climate change to mapping to water. At USGS FAQs you can find answers to the less common questions, such as:

Since we started off with “Fracking”, lets end there: Fracking is an informal name for hydraulic fracturing, an oil and gas well development process that typically involves injecting water, sand, and chemicals under high pressure into a bedrock formation via the well. This process is intended to create new fractures in the rock as well as increase the size, extent, and connectivity of existing fractures.

USGS information can be accessed 24/7 on the USGS FAQ site, and there are Science Information Services staff available from 8AM to 8PM (Eastern) to answer questions by phone at 1-888-275-8747 or by webchat, Monday through Friday (but not on federal holidays). Got questions? ASK USGS!

]]>http://www.usgs.gov/blogs/features/usgs_top_story/have-you-ever-wondered-top-usgs-faqs-for-2014/feed/0Seismographs at the U.S. Geological SurveyLava flows on Mauna LoaOilDrillA drill rig in the Permian Basin of West Texas being used to drill a well which will be hydraulically fractured to produce natural gas. A sound control wall can be seen in the rear of the drill pad to reduce the amount of noise reaching surrounding areas. Photo Credit: Hannah Hamilton, USGSProgress Toward a Safer Future Since the 1989 Loma Prieta Earthquakehttp://www.usgs.gov/blogs/features/usgs_top_story/progress-toward-a-safer-future-since-the-1989-loma-prieta-earthquake/
http://www.usgs.gov/blogs/features/usgs_top_story/progress-toward-a-safer-future-since-the-1989-loma-prieta-earthquake/#commentsFri, 17 Oct 2014 13:18:19 +0000anewmanhttp://www.usgs.gov/blogs/features/?post_type=usgs_top_story&p=203241Read more]]>(Excerpted from USGS Fact Sheet 2014-3092)

Construction on fill and the absence of adequate shear walls contributed to the failure of this structure.

Just minutes before the start of the third game of the 1989 World Series in San Francisco, a magnitude 6.9 earthquake rocked Northern California from Monterey to San Francisco. Centered near Loma Prieta peak in the Santa Cruz Mountains south of San Jose, the quake killed at least 63 people and hospitalized another 350. It destroyed a freeway viaduct in Oakland, dropped a span of the Bay Bridge, collapsed historic buildings in Santa Cruz and apartment buildings in the Marina District of San Francisco, caused extensive damage in Hollister and Watsonville, severed communications, and caused an estimated $6 to $10 billion in property loss. It was the largest temblor to jolt the Bay Area since the Great San Francisco Earthquake of 1906 (magnitude 7.9).

The 1989 Loma Prieta earthquake interrupted several decades of seismic tranquility in the San Francisco Bay Area. It caused damage throughout the region and was a wakeup call to prepare for potentially even more damaging future quakes. Since 1989, the work of the U.S. Geological Survey and many other organizations has improved the understanding of the seismic threat in the Bay Area, promoted awareness of earthquake hazards, and contributed to more effective strategies to reduce earthquake losses. These collective efforts will help reduce the impact of future large earthquakes in the Bay Area.

Since the Loma Prieta earthquake, many organizations, including the USGS, have redoubled efforts to understand earthquake hazards in urban areas and to apply this new knowledge to reduce future losses. The most hazardous areas have been extensively mapped and analyzed, and the most vulnerable structures have been retrofit or rebuilt. The USGS estimates that Bay Area agencies and businesses have invested over $30 billion to retrofit or replace bridges, pipelines, hospitals, municipal buildings, and other infrastructure to make them more earthquake resilient and to reduce the time needed to recover from future Bay Area earthquakes. Communication of earthquake-hazard information to the public, to businesses, and to government agencies has also been strengthened.

Earthquake Likelihood

Even before the 1989 Loma Prieta shock, panels of scientists regularly reassessed the earthquake threat to the San Francisco Bay Area. They currently assign 2-in-3 odds that one or more destructive earthquakes (magnitude 6.7 or larger) will strike the Bay Area in the next 30 years.

Studies conducted since 1989 have added much new information for determining earthquake probabilities. Using airborne laser imagery, geologists have refined maps of earthquake faults. They have uncovered new evidence for the dates and amounts of slip of prehistoric earthquakes on the Hayward, San Andreas, and other active Bay Area faults, and estimated the amount of movement on those faults over past millennia. Using hundreds of continuously monitored GPS receivers and other space-based tools, geophysicists have gained a better picture of the motions of crustal plates that cause faults to accumulate stress and rupture in earthquakes.

Nearly 70 percent of the loss of life and property damage due to the Loma Prieta earthquake stemmed from strong ground shaking, and community managers and scientists alike quickly recognized the need for a better understanding of the most hazardous parts of the Bay Area. In response to the Loma Prieta earthquake, the California Seismic Hazards Mapping Act of 1990 was passed by the California Legislature to assist cities and counties in protecting public health and safety by considering seismic hazards when making decisions concerning land use and development. The act established a statewide urban mapping program to identify areas potentially prone to violent shaking and ground failure. The Bay Area earthquake hazard maps are part of the USGS National Seismic Hazard Maps, which are the basis for significant changes in provisions of the forthcoming 2018 international building code and the national highway-bridge code.

The part of the Cypress freeway structure in Oakland, California, that stood on soft mud (dashed red line) collapsed in the 1989 Loma Prieta earthquake, killing 42 people. Adjacent parts of the structure (solid red) that were built on firmer ground remained standing. Seismograms (right) show that the shaking was especially severe in the soft mud. (USGS photograph by H.G. Wilshire)

Ground Failure

Ground failure—rock falls, landslides, and liquefaction—can locally be more damaging during an earthquake than shaking alone. About 2 percent of the total earthquake- related losses during Loma Prieta were caused by ground failure.

When shaken strongly, unconsolidated sandy deposits that are saturated with water can liquefy. As a result, liquefaction may result in sinking, tilt, distortion, or destruction of buildings and bridges, rupture of underground gas lines and water mains, and cracking and lateral spreading of the ground surface. Since 1989, the USGS has partnered with Federal Emergency Management Agency, Pacific Gas and Electric Company, the San Francisco Public Utility Commission, the City of Oakland, and other agencies to map areas where damaging liquefaction can occur.

The Marina District of San Francisco was heavily damaged in the 1989 Loma Prieta earthquake (left) because it was built on uncompacted, sandy ground in an area with a shallow water table. These conditions caused shaking to be amplified and some areas of ground to liquefy. Shaking collapsed the first story of many apartment buildings and liquefied the ground beneath the sidewalk, causing it to buckle. In the weeks following the quake, the U.S. Geological Survey drill rig shown at right was used to gather subsurface samples so that the causes of liquefaction could be better understood. (USGS photographs by J.K. Nakata and T. Holzer.)

Near-Real-Time Earthquake Information

After the Loma Prieta earthquake, managers of earthquake-monitoring networks in California agreed to combine their data in real time, thereby creating the California Integrated Seismic Network (CISN). The CISN reports within minutes earthquake locations, magnitudes, and ShakeMaps, which show the patterns of shaking across the region, helping community leaders organize emergency crews and relief efforts. The USGS also maps the levels of shaking in different parts of the Bay Area as reported by online respondents through the “Did you feel it?” website and can therefore assess the local intensity of an earthquake independently of ShakeMap. Both maps help emergency responders to rapidly identify locations where damage and need are likely to be greatest.

Example ShakeMap for the Loma Prieta earthquake.This ShakeMap used data recorded in 1989, but it was produced years after the earthquake. Such ShakeMaps are now routinely produced within several minutes of a felt earthquake. Severity of shaking is rated using the Modified Mercalli Intensity (MMI) scale, which ranges from 1 (not felt) to 12 (total destruction).

In 2005, the USGS partnered with the California Department of Transportation (DOT) to produce ShakeCast, an application that estimates the likelihood that a level of shaking will cause damage to a particular structure to prioritize DOT’s inspection of bridges following earthquakes.

In 2010, the USGS released PAGER (Prompt Assessment of Global Earthquakes for Response), an alert that rapidly estimates fatalities and economic losses for earthquakes. PAGER assigns a color code to each potentially damaging earthquake to indicate the level of emergency response the earthquake will require.

Digital seismic instruments now used in the networks report their data within a second, reducing the time for earthquakes to be detected. In fact, advances in technology now permit the computation of earthquake locations and magnitudes within seconds so that notifications can be broadcast to some areas that have not yet undergone shaking from an earthquake—this forms the basis for the Earthquake Early Warning System, which is being developed by the USGS, the University of California at Berkeley, the California Institute of Technology (Caltech), and the University of Washington. It will send alerts to the public and community managers ahead of strong shaking, so that a variety of actions can be taken, such as opening firehouse doors, stopping trains, and taking cover.

Since the 1989 Loma Prieta earthquake, many iconic structures around the Bay Area—including San Francisco City Hall, the Ferry Building, the Golden Gate Bridge, San Francisco General Hospital (above right), and the eastern span of the Bay Bridge (above left)—have been replaced or retrofit with earthquake-resistant support so that they may remain intact in the event of a large earthquake. (USGS photographs by S. Haefner.)

Earthquake Scenarios and Preparedness

Although scientists cannot predict exactly when destructive earthquakes will occur, they can estimate the damaging effects of a potential earthquake of a given size and, together with engineers, assess the expected property damage and loss of life. USGS scientists are working with numerous agencies and organizations to estimate the possible impacts of future earthquakes at both regional and national scales, including scenarios for response exercises for an earthquake on the Hayward Fault and a repeat of the 1906 San Francisco Earthquake.

The regional infrastructure’s poor performance during the Loma Prieta earthquake, coupled with USGS earthquake hazard models, has led several municipalities to require the mandatory retrofit of collapse- prone unreinforced masonry buildings and of “soft-story” buildings. So called because of inadequate support in their first story, collapses of soft-story buildings were prominent in San Francisco’s Marina District during the Loma Prieta earthquake.

The USGS has also partnered with local agencies to assess the dangers to the utilities and transportation corridors around the San Francisco Bay Area. With the San Francisco Public Utility Commission, the USGS mapped the precise location of the San Andreas Fault so that the retrofit of the Hetch Hetchy Aqueduct and water conveyance systems on the San Francisco Peninsula were more resilient. The USGS and Bay Area Rapid Transit (BART), which operates a public rail transit system, estimated the amount of slip that would likely be produced by an earthquake on the Hayward Fault and how it would affect BART’s tunnels crossing the fault.

Communicating Earthquake Hazards

Since the 1989 Loma Prieta earthquake, the USGS and several cooperators have increased their efforts to better communicate earthquake-hazard information to a broad audience. The popular educational booklet called “Putting Down Roots in Earthquake Country” has been translated into Spanish, Chinese, Vietnamese, and Korean in editions entitled “Protecting Your Family from Earthquakes.” All versions are available online. These booklets have been emulated in other highly active seismic regions in the country, including Anchorage, Alaska, Salt Lake City, and the New Madrid region of southeastern Missouri and northwestern Tennessee.

]]>http://www.usgs.gov/blogs/features/usgs_top_story/progress-toward-a-safer-future-since-the-1989-loma-prieta-earthquake/feed/0Structural Failure of HouseCypressFreewayThe part of the Cypress freeway structure in Oakland, California, that stood on soft mud (dashed red line) collapsed in the 1989 Loma Prieta earthquake, killing 42 people. Adjacent parts of the structure (solid red) that were built on firmer ground remained standing. Seismograms (right) show that the shaking was especially severe in the soft mud. (USGS photograph by H.G. Wilshire)MarinaDistrictThe Marina District of San Francisco was heavily damaged in the 1989 Loma Prieta earthquake (left) because it was built on uncompacted, sandy ground in an area with a shallow water table. These conditions caused shaking to be amplified and some areas of ground to liquefy. Shaking collapsed the first story of many apartment buildings and liquefied the ground beneath the sidewalk, causing it to buckle. In the weeks following the quake, the U.S. Geological Survey drill rig shown at right was used to gather subsurface samples so that the causes of liquefaction could be better understood. (USGS photographs by J.K. Nakata and T. Holzer.)LomaPrieta ShakeMapExample ShakeMap for the Loma Prieta earthquake.
This ShakeMap used data recorded in 1989, but it was produced years after the earthquake. Such ShakeMaps are now routinely produced within several minutes of a felt earthquake. Severity of shaking is rated using the Modified Mercalli Intensity (MMI) scale, which ranges from 1 (not felt) to 12 (total destruction).NewBridgeHospitalSince the 1989 Loma Prieta earthquake, many iconic structures around the Bay Area—including San Francisco City Hall, the Ferry Building, the Golden Gate Bridge, San Francisco General Hospital (above right), and the eastern span of the Bay Bridge (above left)—have been replaced or retrofit with earthquake-resistant support so that they may remain intact in the event of a large earthquake. (USGS photographs by S. Haefner.)Preparing Communities for the Next Great Tsunamihttp://www.usgs.gov/blogs/features/usgs_top_story/preparing-communities-for-the-next-great-tsunami/
http://www.usgs.gov/blogs/features/usgs_top_story/preparing-communities-for-the-next-great-tsunami/#commentsTue, 26 Aug 2014 16:11:04 +0000anewmanhttp://www.usgs.gov/blogs/features/?post_type=usgs_top_story&p=201001Read more]]>Typically, USGS Top Stories do not talk about individual contributions to the Survey’s pursuit of providing excellent science for the Nation, but we wanted to take a different path for this particular story. The following narrative highlights the passion of one particular scientist and demonstrates how his research is being used to keep people safe from the next great tsunami.

A Passion for Preparedness

Nate Wood is a geographer with the USGS. And if you live, work, or vacation along the Pacific Coast, he wants to save your life. Nate is part of a team of scientists who assess the vulnerability of U.S. coastal communities vulnerability of U.S. coastal communities around the Pacific Ocean to tsunami hazards. Loosely translated from Japanese for “harbor wave,” a tsunami is a surge of water, or series of waves, pushed from the ocean floor after some event, whether an earthquake, eruption, or landslide, displaces the ocean itself. Tsunamis can either be one of the most destructive forces on earth or may simply dissolve into the daily tide. However, their threat is real and they should never be taken for granted.

Beginning in 1998, Nate began a personal quest to help not only the public, but also emergency managers and first responders better prepare for the inevitability of future tsunamis occurring in the Pacific. Focusing on populations at risk, Nate’s research explores many factors when determining the vulnerability of each community, such as the makeup of the population, access to high ground for evacuations, and viable alternatives like vertical evacuation structures. Using Geographic Information Systems (GIS) technology, Nate combines different land cover, elevation, population, and economic data with tsunami-hazard information to help emergency managers and government officials identify local preparedness and response issues. Relying on a single evacuation plan will not work for all towns along coastal Washington, Oregon, California, Alaska, and Hawaii. Therefore, efforts are placed on creating tailored plans that allow emergency managers and the general public to better understand their respective vulnerabilities and responses, so they can save more lives when the next tsunami comes. This work tackles many of the more controllable aspects of how communities can minimize future losses, rather than focusing on the uncontrollable aspects of where future tsunamis may strike.

When Social Science and Natural Science Converge

The mechanics of tsunamis are relatively well understood. First, a geologic event occurs (e.g., earthquake). This event shifts part of the ocean floor, which displaces a large volume of water. The displaced water travels as a series of waves through the ocean toward the coasts of the surrounding lands. Depending on the size and timing of the waves, certain low-lying areas may become flooded by the surging water. Tsunamis are a unique natural hazard because not only can they be dangerous locally, they can also travel great distances, affecting far-away communities.

Where new research has made strides, is in an approach that merges natural hazards research and evacuation modeling with studies of demographics and human behavioral response to a catastrophe. This type of science in action combines our understanding of the physical processes of tsunamis but places it in the societal context, where community preparedness and evacuations take place. Thus, it allows the scientific research to be much more effective at helping save lives. After all, just because scientists observe a tsunami in the ocean, doesn’t mean people will react and respond to the news appropriately. That’s where understanding human nature, demographics, and geography makes “messaging” of the potential risks and risk-reduction strategies more powerful.

Map showing the time it would take to walk to a safe area in Ocean Shores, Washington, to avoid a tsunami. If a Cascadian Subduction Zone earthquake occurred, the corresponding tsunami could arrive in less than 25 minutes. The black symbols represent proposed vertical evacuation sites, which would offer more people access to closer safe areas.

A Shift in Cultural Awareness

Tsunamis are not a new phenomenon. In fact, there is a geologic record of tsunamis going back millions of years and a historical record of tsunamis affecting coastal areas around the world for as long as people have lived in those areas. What has changed recently is the global awareness of tsunamis and the scientific understanding of the processes, timing, and consequences of this natural hazard, as well as the technological advances that have allowed advance warnings to be issued across the globe. Lately, new research techniques and new avenues of communication have made it easier to share information about who’s at risk, where, and to what degree. For example, because tsunamis are relatively uncommon, sharing experiences between areas where a recent tsunami has occurred with those areas where one is possible has helped promote a greater awareness and preparedness across the globe. Similarly, the global community has also helped clarify and change inaccurate perceptions, such as avoiding the use of the term tidal wave to informing others about ways to spot signs of an impending tsunami. Sadly, yet justifiably, much of this emerging awareness and cultural shift relates back to the December 2004 Sumatra Tsunami, which became the first heavily televised tsunami-related catastrophe, where the loss of human life and destruction was unimaginable. This cultural awareness was further solidified in the public consciousness seven years later during the March 2011 Japan Tsunami.

Building A Resilient Community

From shared experiences, comes shared growth. As part of the evolution of community preparedness planning, emergency planners in the coastal U.S. have begun working with scientists to assess where people are at the greatest risk, as well as what are the best evacuation strategies given the constraints of the local area. Over the years, the USGS has published a series of products aimed at reaching and informing those at risk of natural hazards, such as promotional videos, handouts, fact sheets, and other resources as tools for local emergency management, law enforcement, or community groups to share with the public. After all, no one can prevent a tsunami from occurring, but people can be better prepared for surviving one if they are informed of the risks, warning signs, and escape routes.

Frequent Reminders

Each year, hundreds of earthquakes occur along the Ring of Fire or Pacific Rim. Most of these earthquakes are small and not felt by many people. However, a few of them are big (magnitude 6.5 or greater) and shallowly located. Each of these large-magnitude earthquakes carries with it the potential to unleash a destructive tsunami. The most recent reminder of a potential tsunami threat occurred on June 23, 2014, when a magnitude 7.9 earthquake struck Alaska’s Aleutian Islands. Because it was extremely deep in the Earth’s crust, the earthquake produced only a small tsunami of a few inches. However, for those living along the coast, it brought a swift reminder of the potential that the next big one will come.

Other USGS work on Tsunamis

In addition to Nate Wood’s geographic studies, the USGS also does research into the geophysics of tsunami generation, and the coastal processes of erosion and deposition resulting from a tsunami when it hits land. Basic geological studies of prehistoric tsunamis evidence give scientists an understanding of the frequency and probabilities of future tsunamis.

The USGS also established the Science Application for Risk Reduction (SAFRR) project team, which was created to continue to innovate the application of hazard science for the safety, security, and economic well-being of the nation. After two years of work, on September 4th, 2013, the SAFRR Tsunami Scenario, a scientific report on a hypothetical but plausible tsunami created by a magnitude 9.1 earthquake offshore of the Alaskan peninsula, was released. The report is an analysis of the potential impacts along the California coast, intended for those who need to make mitigation, preparedness, and outreach decisions before tsunamis and those who will need to make rapid decisions during and after tsunamis. The Tsunami Scenario will help them understand the context and consequences of their decisions that can improve preparedness and response.

]]>http://www.usgs.gov/blogs/features/usgs_top_story/preparing-communities-for-the-next-great-tsunami/feed/0Ocean ShoresMap showing the time it would take to walk to a safe area in Ocean Shores, Washington, to avoid a tsunami. If a Cascadian Subduction Zone earthquake occurred, the corresponding tsunami could arrive in less than 25 minutes. The black symbols represent proposed vertical evacuation sites, which would offer more people access to closer safe areas.Magnitude 6.0 Earthquake in Californiahttp://www.usgs.gov/blogs/features/usgs_top_story/magnitude-6-0-earthquake-in-california/
http://www.usgs.gov/blogs/features/usgs_top_story/magnitude-6-0-earthquake-in-california/#commentsSun, 24 Aug 2014 13:14:58 +0000Scott Horvathhttp://www.usgs.gov/blogs/features/?post_type=usgs_top_story&p=200941Read more]]>

Location of the M6.0 – 6km NW of American Canyon, California that occurred on August 24, 2014.

A magnitude 6.0 earthquake struck in northern California on August 24, 2014 at 10:20:44 UTC. Visit the USGS event page to learn more about this earthquake. This event is being called the South Napa earthquake.

The USGS and its partners are working to develop a prototype Earthquake Early Warning System for the West Coast of the United States called ShakeAlert. The system could provide seconds to minutes of warning before strong shaking. Imagine if doctors could stop procedures before an earthquake. Or if emergency responders had a few extra moments to act, trains could be slowed or stopped, airplane landings could be redirected, and people could move to safer locations. Learn more by visiting the USGS website on this project.

]]>http://www.usgs.gov/blogs/features/usgs_top_story/magnitude-6-0-earthquake-in-california/feed/0M6.0 – 6km NW of American Canyon, CaliforniaLocation of the M6.0 - 6km NW of American Canyon, California that occurred on August 24, 2014.20 Years Ago, Northridge Started Revolution in Quake Sciencehttp://www.usgs.gov/blogs/features/usgs_top_story/20-years-ago-northridge-started-revolution-in-quake-science/
http://www.usgs.gov/blogs/features/usgs_top_story/20-years-ago-northridge-started-revolution-in-quake-science/#commentsFri, 17 Jan 2014 18:30:10 +0000anewmanhttp://www.usgs.gov/blogs/features/?post_type=usgs_top_story&p=189471Read more]]>

Beginning at 4:31 a.m., the ground shook intensely for 10-20 seconds, awakening area residents to one of the most devastating quakes in U.S. history.

At 4:31 a.m. on January 17, 1994, one of the most costly earthquakes in U.S. history struck northwest of downtown Los Angeles. The Magnitude 6.7 Northridge earthquake and its aftershocks (including two that were greater than M6.0) caused 57 fatalities, more than 9,000 injuries, and an estimated $20 billion in damage. About 20,000 people were left at least temporarily homeless. Yet some seismologists believe that Northridge was “a near miss” that could have been much worse. In the 20 years since Northridge, how has earthquake science advanced to protect against such devastating quakes—or an even more devastating “direct hit”?

Infrastructure took a major hit in the Northridge quake, leading to efforts to improve monitoring for rapid damage assessments at key infrastructure facilities via USGS ShakeCast.

Improved Monitoring and Reporting

Before the 1994 Northridge quake, only seven digital seismic monitoring stations were in place throughout Southern California; all other stations were low-bandwidth analog recorders. With these limited seismic stations and only three computers to process the data, it could take scientists as long as 45 minutes to precisely identify an earthquake epicenter and magnitude. It took even longer—as much as two months—to develop maps showing the intensity of ground shaking.

A USGS seismologist conducting a field survey in the aftermath of the Northridge quake. Today, the instruments of the Plate Boundary Observatory continuously monitor earth crust movement and transmit that data to scientists for analysis.

Today, the Southern California Seismic Network is an integral part of the USGS Advanced National Seismic System with 400 digital monitoring stations that provide real-time information to identify an earthquake’s location and to assign a preliminary magnitude. ShakeMap maps of ground shaking intensity are now developed and available on the web within minutes rather than months. The ShakeCast service transmits ShakeMaps within minutes to operators of key infrastructure facilities such as power plants and water lines. These rapidly available data and products provide emergency managers with invaluable tools to assess damage and to know when, where, and how to respond.

While scientists still conduct post-earthquake surveys to characterize the slip that occurs along fault ruptures, the USGS cooperated with the National Science Foundation, the UNAVCO Consortium, and several research universities to establish the Plate Boundary Observatory (PBO). A key element of NSF’s EarthScope program, PBO includes a network of global positioning system devices and strainmeters that continuously monitor motions of the Earth’s crust, and transmit data about tectonic plate movement and strain.

The shake map was “recreated” years after the fact. Today, they are done automatically and on the fly.

The USGS has taken advantage of Internet and social media advances to improve the public’s ability to communicate and learn about earthquakes. Earthquakes from around the globe are reported within minutes on the USGS earthquake website. Did You Feel It? lets citizens report their own observations of earthquakes they experience. The Tweet Earthquake Dispatch sends out earthquake alerts to two Twitter accounts: @USGSted and @USGSBigQuakes.

Improved Understanding of Earth Processes

The Northridge earthquake occurred on a previously unidentified “blind” thrust fault, a fault hidden below the urban area, which didn’t break all the way through to the Earth’s surface. Since 1994, the USGS and its research partners have vastly improved our scientific understanding of the subsurface structures and processes affecting the Los Angeles basin and other areas at risk from earthquakes.

Even before the Northridge quake, scientists from the Southern California Earthquake Center (SCEC), the USGS, and other organizations had begun the Los Angeles Region Seismic Experiment to collect seismic images of the Earth’s crust beneath the region. These “pictures” of subsurface structures (similar to CAT scans), along with other geologic and seismic data collected, helped scientists begin to develop a sophisticated three-dimensional model of southern California faults and geology. With subsequent improvements in monitoring capabilities and tremendous advances in computational capabilities, a number of other data sets have been incorporated and these models have been refined over the last several years.

Example map from the SCEC Community Fault Model

SCEC provides open access to these and other models. The Community Fault Model includes about 140 faults in southern California that host most of the area’s earthquakes. Some of the faults included in the model had not yet been identified when the 1994 Northridge quake occurred. The SCEC Community Velocity Model includes a representation of the crust and upper mantle geologic structure in southern California for use in fault systems analysis, strong ground motion prediction, and earthquake hazards assessment. The Community Velocity Model shows where earthquake waves travel at different rates and is used to make predictions of shaking intensity for ruptures along different faults.

These research advances were coupled with improved data integration. Multiple datasets collected by different scientists have been combined and interpreted together to provide an integrated picture of the earth beneath the Los Angeles area.

Improved Cooperation

While the USGS is a leader in earthquake monitoring and research, the advances since Northridge could not have occurred without strong partnerships with other research institutions, state emergency managers, and local governments. The extensive damage left by the Northridge quake showed the need for closer cooperation among scientists, engineers, and other stakeholders to reduce risk and increase community resiliency.

At the federal level, the USGS is a partner in the four-agency National Earthquake Hazard Reduction Program. In California, the USGS is a member of the California Integrated Seismic Network. CISN supports earthquake scientists, structural engineers, and emergency managers with monitoring and research. Working together with the State of California and other entities, USGS seismologists have developed fault location products that help city planners easily identify vulnerabilities caused by proximity to earthquake faults. MyHazards, a web tool that allows users to enter a California address and see earthquake related hazards, and an updated series of fault location maps, produced by the California Geological Survey, allow users to improve their situational awareness, and take appropriate actions to prepare for the next big earthquake.

The USGS also provides scientific support for community earthquake awareness. Millions of Californians participate in ShakeOut earthquake drills and practice Drop, Cover, and Hold On.

]]>http://www.usgs.gov/blogs/features/usgs_top_story/20-years-ago-northridge-started-revolution-in-quake-science/feed/0Northridge, CA Earthquake DamageNorthridge, CA Earthquake DamageNorthridge, CA Earthquake DamageShake MapThe shake map was “recreated” years after the fact. Currently they are done automatically and on the fly.Northridge Earthquake MapSubsurface structuresUSGS Works Toward Seismic Safety in Burmahttp://www.usgs.gov/blogs/features/usgs_top_story/usgs-works-toward-seismic-safety-in-burma/
http://www.usgs.gov/blogs/features/usgs_top_story/usgs-works-toward-seismic-safety-in-burma/#commentsMon, 29 Oct 2012 16:59:11 +0000Scott Horvathhttp://www.usgs.gov/blogs/features/?post_type=usgs_top_story&p=175329Read more]]>The country of Burma straddles a complex and highly active earthquake zone — the junction between the Himalayan front to the northwest of the country and, to the south/southeast, the subduction zone responsible for the enormous magnitude-9.3 Sumatra earthquake and ensuing tsunami of 2004. A record of damage to ancient and beautiful pagodas throughout Burma’s cities and countryside attests to the past occurrence of major earthquakes. Few of these damaging earthquakes, however, have occurred during the 20th century. There is an urgent need for steps to mitigate earthquake risk in Burma, as it is not a question of “if” future large earthquakes will occur, but rather “when.” With our knowledge of earthquakes, it is certain that significant earthquake disasters will occur in the country’s future, and earthquake hazards remain poorly characterized. Exacerbating the concern, southern Burma, including the country’s most populous city, Rangoon, sits on the Irrawaddy Delta, underlain by a thick blanket of soft sediments that would significantly amplify earthquake shaking.

The Schwedagon pagoda, Burma’s most revered shrine, has been damaged multiple times by earthquakes throughout its long history.

As Burma’s government moves forward with political and economic reform, it has also shown greater openness to working with U.S. government agencies on a variety of issues. The U.S. Geological Survey is using this opportunity to work with seismology and disaster management experts to help design a long-term disaster risk reduction program for Burma that will assess seismic hazard and take steps to reduce risk. As a first step to launching this project, USAID’s Office of Foreign Disaster Assistance (OFDA) sponsored an initial visit May 21-25, 2012, by USGS research geophysicists Susan Hough and Mark Petersen and USAID/OFDA regional adviser Brian Heidel.

The U.S. government team met with counterparts from the Burmese government, including the Department of Meteorology and Hydrology and the Ministry of Social Welfare, Relief, and Resettlement, as well as United Nations agencies and nongovernmental organizations such as the Myanmar Earthquake Commission and the Myanmar Engineering Society. The visit culminated with a lively half-day Earthquake Preparedness Planning workshop that was well-attended by key staff from all of the above-mentioned groups.

The May 2012 visit focused on an assessment of needs and gaps in current earthquake risk-assessment programs. Through meetings and site visits, the U.S. team identified high-priority future program activities that will be addressed by future USAID/OFDA-supported USGS missions. Most importantly, the visit laid a foundation for future collaboration between the United States and Government of Burma aimed at mitigating earthquake risk. As Burma enters a new period of economic expansion and potentially rapid construction growth, these steps will be of vital importance to help ensure that the earthquake resilience of Burma’s future development will match the enormous resilience of its people.

Over the next few days, the USGS will be deploying portable seismometers around northern Virginia in order to better characterize and monitor all aftershock activity and to better define the fault zone from which Tuesday’s earthquake originated.

New Zealand has experienced another damaging earthquake close to the city of Christchurch, which is still recovering from the magnitude-6.1 earthquake that struck in February. This latest quake has resulted in additional damage to buildings and infrastructure.

]]>http://www.usgs.gov/blogs/features/usgs_top_story/preliminary-magnitude-8-9-near-the-east-coast-of-japan/feed/0landsat_japanLandsat data, acquired by the U. S. Geological Survey on March 20, 2011 show the Sendai, Japan region.